Several communications systems, including magnetic recording channels, experience inter-symbol-interference (ISI). In general, a channel detector is employed to recover ISI channel inputs. Usually, a maximum-a-posteriori (MAP) detector or soft output Viterbi algorithm (SOVA) is used as the channel detector. Both detectors compute soft information (likelihood information) which might be used by an outer error correction code.
In order to improve reliability of communication systems, conventional systems employ different error correction codes. Among these, a Low Density Parity Check (LDPC) code is an excellent error correction code (ECC). The LDPC codes can be applied to a variety of communication systems, including magnetic recording channels.